<html>
    <head>
        <title>
            内外边距
        </title>
    <style>
        #d1 {
            border: 1px solid;
            background-color: aqua;
            width: 100px;
            height: 100px;
        }
        #d2 {
            background-color: aquamarine;
            width: 50px;
            height: 50px;
           /*
            margin-top: 25px;
            margin-left: 25px;
            */
            margin :10px 20px 30px 40px;

        }
        
        table , td, tr{
            border: 2px solid ;color: black;
            width: 500px;
            height: 50px;
            border-collapse: collapse;  
            vertical-align: middle;
            text-align: center;
        }
        tr:hover {
            background-color:aliceblue ;
        }
        #d1 {
            ba
        }
    </style>
    </head>
    <body>
        <div id="d1">
            <div id="d2"></div>
        </div>
        <ul>
            <li>1</li>
            <li>2</li>
            <li>3</li>
        </ul>
        <table>
            <tr>
                <td>姓名</td>
                <td>年龄</td>
                <td>成绩</td>
            </tr>
            <tr>
                <td>张三</td>
                <td>12</td>
                <td>70</td>
            </tr>
            <tr>
                <td>李四</td>
                <td>14</td>
                <td>80</td>
            </tr>

            <div id="d1"></div>
            <div id="d2"></div>
            <div id="d3"></div>
        </table>
       
    </body>
</html>